Process for producing methylene-diamilines



Nov. 11, 1969 J oss ET AL 3,478,099

PROCESS FOR PRODUCING METHYLENEDIAMILINES Original Filed Feb. 28, 1964No OH SOLN NEUTRALIZER CONVENTIONAL SEPARATION 2 I! p o N 5: E 0 0 O Q NO k E 2 I W E 2 Q 2 WM INVENTORS:

z RICHARD J. ROSS I: BY GEORGE M. FOHLEN United States Patent 3,478,099PROCESS FOR PRODUCING METHYLENE- DIAMILINES Richard J. Ross, WalnutCreek, and George M. Fohlen,

Millbrae, Calif., assignors to Kaiser Aluminum & Chemical Corporation,Oakland, Calif., a corporation of Delaware Continuation of applicationSer. No. 348,103, Feb. 28, 1964. This application Sept. 9, 1966, Ser.No. 594,954

Int. Cl. C07c 87/50 US. Cl. 260--570 9 Claims ABSTRACT OF THE DISCLOSUREA continuous process for producing poly primary aromatic amines fromaniline and formaldehyde comprising admixing a strong mineral acid suchas hydrochloric acid and aniline, to neutralize the aniline (at leastabout thereof) to form the corresponding anilineacid salt, continuouslyviolently mixing the aniline-acid admixture with the aldehyde at atemperature not over the boiling point of any of the constituents for ashort time, withdrawing the resultant reaction mixture to a secondreaction zone and maintaining it there with gentle agitation at fromabout 80 to 105 C. until the aniline is substantially all reacted,withdrawing from the second reaction zone and neutralizing with analkali metal hydroxide to form the alkali metal salt of the acid and torecover a water-immiscible organic phase containing the aminecondensation product.

This application is a continuation of application Ser. No. 348,103,filed Feb. 28, 1964.

This invention relates to a process for the production of poly primaryamines; and more particularly, it relates to a continuous process forproducing such products by condensation of an aldehyde and an aromaticprimary amine such as aniline.

Polyamines are useful materials in their own right and can be preparedin the form of resinous materials that can be generally classified asplastics. However, the poly-primary amines have recently beenparticularly useful as intermediates in the formation ofpoly-isocyanates which in turn are useful in the production ofpolyurethanes. For this particular purpose poly-primary amines areparticularly beneficial in that phosgenation of such primary amines willresult in the desirable polyisocyanate product that is useful inpolyurethane production. The poly-primary amines that are especiallyuseful, are those containing from at least about 20% diamine, andsubstantially all of the rest, if any, higher condensation products,such as the triamine and tetramine. In the condensation of mononucleararomatic primary amine, e.g. aniline, and an aldehyde, the product willhereinafter be termed diamine, e.g. as when two molecules of anilinecondense with formaldehyde to form NH -C H -HCH-C H -NH Similarly whenthree molecules of aniline condense with two molecules of formaldehydethe product is termed herein triamine,

Also in a similar manner, when four molecules of aniline condense withthree molecules of formaldehyde the 3,478,099 Patented Nov. 11, 1969product is termed the tetramine, and so on. Such condensation productsare herein termed, broadly, polyprimary amines. In other Words,polyamines according to the present invention are the poly-primaryamines wherein the condensation is effected through a hydrogen on anuclear or ring carbon. Of such polyamines, the diamines are preferablycondensed through the para position with respect to the amine portion ofthe aromatic primary amine molecule. To obtain such nuclear condensationit has hitherto been found necessary in processes where preliminarymixing of reactants has been done under neutral or mildly acidicconditions, to maintain the reaction product of aniline, for example,and the aldehyde at a high temperature and in astrong acid environmentfor a prolonged period of time, e.g. for over five hours, therebyrearranging the molecules so that they change to primary aminesconnected through the aromatic nucleus rather than the nitrogen atom.

In many former proposed processes, the acidified formaldehyde was mixedwith the aniline and there ensued an uncontrollable reaction, due to thecombined exothermic effects of neutralization and also of thecondensation reaction. In fact, the concentration of resinous materialsin such processes becomes so great in some instances that the entirereaction product was solid. This is a great disadvantage Where furtherspecific reactions are desired; and, for instance, phosgenation to adesired polyisocyanate is not then feasible. Products made by prior artbatch-Wise processes have a larger proportion of the higher condensationproducts for a given anilinealdehyde ratio than the product made in acontinuous fashion according to the present invention. Formerly, forinstance, the acidified aldehyde was added gradually to the aniline andthe later portions of the aldehyde could react with some condensationproducts in the mixture as well as with some unreacted aniline.

The present invention provides a process which largely mitigates orcompletely avoids the above-mentioned difiiculties. The process of thepresent invention is at such a controlled rate that it can be effectedcontinuously without any substantial formation of undesired endproducts, such as resinous materials. Additionally, the process of thisinvention is maintained effected rapidly with the condensation reactionsbeing largely directly on the nucleus so that little rearrangingreaction is required. Even further, the reaction of this invention isselective, and can be controlled to convert a major portion of theaniline to the valuable primary diamine rather than to a more randomdistribution of polymers that is typical of and a disadvantage of priorart processes.

The process of the present invention comprises first mixing or blendinganiline with an aqueous strong mineral acid, preferably hydrochloricacid. Sufficient acid is admixed to react with at least a portion orwith all of the aniline to form aniline hydrochloride. Preferably, forbest operation of the process, there is admixed sufficient acid to soreact with from about 20 to about mol percent of the aniline. In apreferred operation, the admixture so formed has a pH of about from 3.5to 4.5. In one embodiment of this invention there is admixed with theaniline-acid mixture a neutral organic liquid which has a solvent actionon the components of the reacted mass, such as a hydrocarbon,chlorinated hydrocarbon or the like, in an amount up to about 10 partsper parts aniline, which has been found advantageous in some modes ofoperation in maintaining all components in solution and preventingundesired precipitation of any component on the walls of the system asthe reaction proceeds in the continuous process.

The aniline-acid blend, with or without a neutral organic liquid, isthen rapidly and thoroughly mixed with the aldehyde in a first-stagereaction zone which is cooled and provided in any desired manner, withmeans for insuring thorough intermixing and cantact between the variousingredients. The temperature in the first reaction zone tends to risebecause the reaction effected therein is exothermic and cooling usuallyis provided to maintain a suitable temperature. However, no criticaltemperature exists for the reaction as long as it is maintained belowthe boiling point of any of the reactants or reaction products therein.Preferably, the temperature maintained in the first reaction zone isfrom 20 C. to 100 C. The reaction mixture is suitably held in the firstzone for from about 15 seconds to about 2 minutes with intimateintermixing of the ingredients during the whole period. In order toensure thorough mixing, violent agitation is preferably effected in thisstage. In carrying out the reaction in one embodiment it is advantageousthat the inlet for the formaldehyde, for example, be so arranged that itis maintained out of contact with the liquid in this zone to avoidplugging of such tube which tends to occur because of the rapidity withwhich these components react.

The efiluent from the first reaction zone is passed to a second reactionzone. In this zone, gentle agitation is suflicient. The second reactionzone is provided to give the reactions time to go to completion. In thefirst reaction zone several side reactions, i.e. other than coupling oftwo anilines by a methylene group, such as reaction through one or bothof the amine nitrogens of the aniline molecules, for instance, takeplace to a small extent. The resultant molecule, of the last-mentionedreaction, a secondary amine, is rearranged to form the desiredpoly-primary amine in the presence of an acid medium is permitted asuitable holding period. Another product issuing from the first reactionzone is an aminobenzyl alcohol or polymers thereof. These latterproducts when maintained or held in an acid medium in the secondreaction zone condense and rearrange to form the desirable poly-primaryamines and this reaction, too, goes substantially to completion in theholding period in the second reaction zone. Such holding is maintaineduntil the admixture shows no further reaction of or reduction in theamount of aniline. This is easily determined by testing a sample of thereaction mixture in the known manner for free aniline. Whensubstantially no further reduction in the amount of free aniline isshown, the rearrangement or second-stage reaction of the presentinvention is completed. Under the preferred conditions shown herein,such holding period is about one hour. However, regardless of the mannerin which the reactions take place, it has been found that employing thesequence of process steps described and claimed herein will produce thedesirable result of converting aniline and an aldehyde substantiallycompletely to the poly primary amine condensation product.

The second reaction zone is maintained at a temperature of from 80 C. upto boiling point of the mixture, preferably at from 80 C. to 105 C. Thereactions effected therein have been found to be slightly endothermicand a small amount of heat is therefore supplied to the reaction zone.Following the residence time in the second reaction zone, the reactionproduct issuing from the second zone is neutralized and separated intoits component phases by conventional means. In other words, at the endof this reaction or rearrangement step, the reaction mass is neutralizedby addition of caustic soda which causes formation of a two-phase systemcomposed of an aqueous phase and an organic phase, and the desiredproducts are recovered from this system in the conventional manner.Suitably, there is added to the effluent from the second reaction zonesuflicient aqueous NaOH to react with the .4 HCl, mostly present in theform of polyamine hydrochloride, and to form sodium chloride whichdissolves in the Water of the aqueous phase. The two-phase system istreated in any desired manner to separately recover the desiredpolyamine product. In one embodiment, the twophase system issuing fromthis zone is subjected to steam distillation to strip off unreactedaniline and the remaining material comprises an organic phase containingprincipally poly-primary amine and an aqueous phase containing NaCl.Advantageously, a suitable organic liquid solvent as describedhereinabove, e.g. monochlorbenzene, is admixed therewith to dissolve thepoly-primary amine product, and the resultant two-phase system isseparated, the aqueous phase being discarded. The organic phase sorecovered can be suitably washed with water and the solvent is distilledoff to recover the polyamines product as residue. If desired, thesolution itself can be employed in further reactions.

Miscellaneous condensation reactions between aniline and an aldehyde inthe presence of a strong mineral acid are effected so readily thatrunaway temperatures and uncontrolled reactions are difiicult to avoid.This characteristic of the reactions in fact contributes largely to thedifficulty of effecting a successful continuous commercial process forthe production of poly-primary amines. The present invention providessuch a continuous commercial process in that it controls the rate notonly to promote the formation of poly-primary amines, but also to retardthe undesirable secondary reactions.

In the present invention, a continuous process is provided whereinaniline and acid are first pre-mixed and the heat or neutralization thusproduced is dissipated prior to effecting the reaction between anilineand aldehyde. Thus, in the first reaction zone only one exothermicreaction is effected and temperature control is substantially easier tomaintain.

Employing the preferred range of neutralization of aniline also isadvantageous in providing a successful continuous process. It has beenfound that when 20 to 70 mol percent of the aniline is neutralized priorto mixing aldehyde, the diamine is formed in the para position therebyproducing the desirable para di-primary amine. If less than 20 molpercent of the aniline is neutralized with acid in the reaction mixture,the reaction rate with aldehyde is slow; and when more than 70 molpercent of the aniline is neutralized there is greater tendency to earlyprecipitation of the aniline salt, causing operational difliculties.

The aldehydes that can be employed in this invention are those normallyused in producing polyamines and are preferably the lower molecularweight aliphatic water soluble aldehydes, i.e. containing less than 8carbon atoms, and aromatic aldehydes and mixtures of these with eachother. By way of example only, such aldehydes as formaldehyde,acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde,benzaldehyde and furfuraldehyde can be employed.

In another aspect this invention includes modifying the productcomposition by regulating the ratio of reactants. The amount of diaminein the product can be controlled by regulating the ratio of aldehyde toaniline. Thus, in the specific case of aniline and formaldehyde, whenthe mol ratio of aniline to formaldehyde is 4 to 1.9 or 2.1:1, a productcontaining 70 wt. percent diamine is obtained while when the ratio ofaniline to formaldehyde is 4 to 3.2 or 1.25 :1, the product will containabout 10 wt. percent diamine. Thus it is preferred to employ a mol ratioof aniline to formaldehyde of from 1.25:1 to 2.1:1, in this specificmode of operation employing these two reactants.

The accompanying drawing is a schematic representation of one specificembodiment of the invention in the production of the poly primary amineby the condensation of aniline and formaldehyde, to be described inconjunction with the drawing, and both the drawing and the process areintended herein as being illustrative only of the invention.

The embodiment illustrated herein will be described in regard to thepreferred reactants of this invention, aniline and formaldehyde. Acontainer for aniline and a container 11 for hydrochloric acid dischargethrough lines 12 and 13 respectively and join in line 15 which passes toa blender 16. The blender contains a cooling means illustrated as coil17 through which flows a cooling medium such as water, and an agitator18 to insure that the material in the vessel 16 is thoroughly mixed andblended. The aniline-hydrogen chloride mixture of the compositiondescribed above produces heat of neutralization which is removed in thecooling water, and the mixture is maintained in this example at atemperature of less than 40 C. Cooling can also be effected ortemperature controlled by introducing cold starting materials intoblender 16 so that the heat of neutralization will bring the temperatureof the mixture up to that desired. However, a high or boilingtemperature in the mixture passing from the vessel 16 desirably isavoided.

The aniline-acid mixture is passed from vessel 16 through line 20 intothe top of first-stage reactor 21. Formaldehyde from a storage vessel 22is passed through line 23 into the top of first-stage reactor 21. It ispreferred that the formaldehyde be introduced in such manner, e.g.through a vapor gap, that it does not react with the acidified anilineat the point of entry, because solids may form there to block the pipemonth. In this embodiment, reactor 21 is an in-line mixer which mayamount to substantially no more than a small diameter pressure vessel oreven a large pipe with jackets 25, 25 and provided with means forintroducing and removing a cooling medium shown as 27, 27 and 28, 28respectively. The mixing means 26 provided in reactor 21 is shownschematically here as a motor-driven series of impellers. However, othermeans of creating conditions of turbulent flow can be employed.

In this embodiment, the first zone, A, of reactor 21 is a preferablymixing zone wherein the aniline-containing admixture and theformaldehyde are rapidly and vigorously mixed and the temperature inthis zone is maintained at not over about 40 C., to retard reactionuntil the ingredients have been thoroughly interdispersed. The coolingjacket is therefore preferably provided with its own inlet and outletmeans to enable thorough cooling and temperature control as desired. Theresidence time in this zone, in the continuous process is very short,not usually exceeding about 10 seconds. The mixture then is conducted,or flows, onward to the next portion of reactor 21, shown in the drawingas zone B, wherein vigorous agitation is also effected, e.g. by means ofimpellers 26, and where the temperature is maintained, for instance, atabout 60 C. to 70 C. The residence time in reactor 21 is between 70 and75 seconds on the average in this embodiment. The cooling medium flowingthrough jacket 25 is sufiicient to maintain the temperature constant atany level lower than the temperature at which methanol will boil fromthe mixture in the methanol is an ingredient of the formaldehyde stream,formaldehyde being generally used in the form of formalin which is asolution of methanol, water and formaldehyde. Alternatively, reactor 21can be formed as a two-stage system having an initial mixing stage inwhich the aniline-acid stream is thoroughly and violently blended withthe formaldehyde stream and is then conducted to a longer contactingstage in which intermixing and contact is less vigorous or more gentle.

The reaction product passing through line 30 from the reactor 21 willconsist largely of the poly-primary amines but it will contain somesecondary amine, some alcohol, some unreacted aniline, formaldehyde andhydrochloric acid. This reaction mixture passing through line 30 enterssecondary reactor 31 which has sufiicient capacity to provide the streamwith a residence time of at least one-half hour. The reactor 31 is alsoprovided with a heating means 32 in that the final reactions eifected inreactor 31 are slightly endothermic. The temperature in this reactorpreferably is maintained at -100 C. which is readily accomplished, e.g.by passing steam through the heating means 32 at slightlysuperatmospheric pressure and at a sufficient rate to maintain thetemperature at the desired level, or by steam injection, if desired. Thefinal reactions effected in the secondary reactor 31 have atime-temperature relationship and are effected more quickly at a highertemperature. The second reaction zone can also function at highertemperature when under superatmospheric pressure.

reactor 31 through line 33 passes to a neutralizer 35 into which sodiumhydroxide is introduced through line 36. In the neutralizer, thehydrochloric acid is neutralized by the caustic soda to form sodiumchloride and the mixture of organic reaction products and aqueous brinepasses through line 37 to conventional separation means shownschematically at 38. The aqueous brine solution formed by neutralizinghydrochloric acid with sodium hydroxide solution causes separation outof the poly-primary amine product along with any unreacted aniline andorganic solvents that are employed so that the separation of the aqueousphase from the organic phase is readily effected. The further separationprocesses described above are conventional in the art of recovering thepoly amine condensation product of aniline and formaldehyde bypreviously known methods and will not be described in further detailherein.

As a specific example of the process of this invention, an anilinehydrochloride feed was prepared by mixing 39.4 parts by weight of 20 B.aqueous HCl and 60.6 parts by weight aniline. To this mixture 5 parts byweight of monochlorobenzene were added and the mixture was cooled to 37C.

The other reactant employed was formaldehyde which was used in thecommercially available form known as formalin, a blend of about 37% byweight formaldehyde, 842% by weight methanol and the remainder water,but formaldehyde free of methanol is preferred, for great er ease ofoperation.

The aniline-acid solvent mixture was pumped into a mixing zone where itwas violently mixed with formaldehyde with a high speed impeller for 7seconds and at a temperature of not over 40 C., and then passed to firstreactor or reaction zone where a rotating rod maintained turbulence andgood mixing for an additional 40 seconds. A water jacket surrounding thefirst reaction zone was regulated to maintain the temperature constantas indicated in Table I.

The effluent from the first reaction zone was passed to a secondreaction zone which was jacketed to heat it with steam and maintain thetemperature in the reaction zone at 95 to C. and which had sufiicientcapacity to hold the eflluent from the first reaction zone for a periodof approximately one hour. At the end of this period about 312%, basedon total weight of reactor eflluent, of unreacted aniline remained inthe reaction mixture.

With the product from the second reaction zone there is admixed asufficient amount of strong aqueous NaOH solution to react with all ofthe HCl present to form NaCl and preferably to bring the reactionmixture to a pH of from 8.5 to 11.0. At this time, the reaction mass ormixture separates into two liquid phases, of which one is an aqueousphase and one is an organic phase. The Water-soluble components,principally sodium chloride, go into the water phase; and the organicphase contains substantially all of the desired polyamine products, anyorganic liquid solvent which may have been added, which solvent in thisexample is monochlorbenzene, any unreacted aniline and any othercomponent soluble in the solvent. The Water and organic phases areseparately recovered in any desired manner and are further worked up asdesired. In particular, the polyamine product is recovered as describedhereinabove.

In a series of tests carried out as described above wherein the molratio of aniline to formaldehyde and the temperature in the firstreaction zone are varied as described in Table I below, and the otherconditions are as set forth in the example above, the very good yield ofdiamine, NH -C H CH -C H -NH in this continuous and rapid process isclearly demonstrated. The remainder of the final product consistsessentially of triamine and tetramine.

TABLE 1 Diamine, wt.

M01 ratio First reactor, percent of final Aniline:Formaldehydo temp., 0.product As indicated by the table a higher ratio of aniline to aldehydehas been found to result in an increased amount of diamine in theproduct. The total polyamine product is suitable for many uses, forexample, for suitable reaction to produce isocyanates, or as rubberadditives, curing agents for epoxy resins, etc.

By the present process the two reactants are introduced into thereaction zone in certain proportions, as defined herein, therebyenabling controllable production of the condensation products in thedesired distribution, or relative amounts. Furthermore, the presentprocess enables addition of the reactants in the desired proportions orratios instantaneously and in a continuous manner.

In the present specification and claims, the term aniline is intended toinclude aniline itself, NH -C H and also substituted anilines whereinnuclear or ring hydrogen is substituted by a halogen or a low molecularweight aliphatic group which does not intefere with the condensationreaction, for example, ortho-toluidine, o-chloroaniline, trifiuoromethylaniline, halogenated aniline. It is also to be understood that althoughthe above specific description has been given with respect tohydrochloric acid, other aqueous strong acids such as nitric or sulfuricacid, can alternatively be employed. Other devices than thosespecifically described herein can be used for carrying out the reactionsof this invention. The reactions can be carried out at atmosphericpressures, but, if desired, increased or superatmospheric pressures canbe suitably employed; but it is generally economical and advantageous tocarry out the process at atmospheric pressure. In the neutralization ofthe eflluent from the second reaction zone, caustic alkali or alkalimetal hydroxide other than caustic soda can be employed, e.g., potassiumhydroxide, ammonium hydroxide or sodium carbonate, but NaOH iseconomical and advantageous in case of use and is pre ferred. In thisspecification and claims, percentages given are by Weight unlessotherwise specified. Other mean of ensuring thorough intermixing of thevarious components than those specifically shown herein can be employed.Other apparatus, e.g. a continuous pipe system or tubular reactorprovided with suitable control means and if desired turbulent flow meanscan alternatively be employed.

Having now described the invention, what is claimed is:

1. In a continuous process for the production of poly primary aromaticamine condensation product from aniline and formaldehyde, the stepswhich comprise admixing aqueous strong mineral acid and aniline, saidacid being admixed in an amount sufficient to neutralize at least aboutof said aniline to form the corresponding aniline-acid salt, admixingthe resultant aniline-acid admixture with formaldehyde in a firstreaction zone with continuous violent mixing at a temperature not overthe boiling point of any of the constituents of the reaction zone,maintaining said aniline-acid admixture in said first reaction zone withvolent agitation for a period of from about 15 seconds to about 2minutes, withdrawing the resultant reaction mixture from said firstreaction zone as efiluent and passing to a second reaction zone,maintaining said reaction mixture in said second zone with gentleagitation until substantially no further reaction of aniline occurs,maintaining the temperature of said second zone at from about C. toabout 105 C., withdrawing the reaction mixture from said second reactionzone as effluent, and admixing therewith an alkali metal hydroxide toreact with all of the said mineral acid present to form the alkali metalsalt thereof and to form an aqueous phose and a water-immiscible organicphase and separately recovering said organic phase.

2. A process as in claim 1 wherein first reaction zone is maintained ata temperature of from 20 C. to 100 C.

3. A process as in claim 1 wherein said second reaction zone ismaintained at a temperature of from C. to C.

4. Processes as in claim 1 wherein the mol ratio of aniline toformaldehyde is from 1.25 :1 to 2.1:1.

5. A process as in claim 1 wherein the effluent from said secondreaction zone is neutralized with aqueous sodium hydroxide solution.

6. A continuous process for the production of poly primary aromaticamine condensation product from aniline and formaldehyde which comprisesadmixing aqueous hydrochloric acid and aniline, said acid being admixedin an amount sufficient to neutralize from about 20 mol percent to about70 mol percent of said aniline to form aniline hydrochloride,incorporating in said mixture from 2.5 to 5.0 parts monochlorbenzene per100 parts aniline, introducing said admixture into a first reactionzone, introducing into said first reaction zone an amount offormaldehyde to provide a mol ratio of said aniline to said formaldehydefrom 1.25 :1 to 2.111, thoroughly and violently intermixing saidreactants and maintaining the temperature in said reaction zone atbetween 20 C. and 100 C., maintaining said reactants in said firstreaction zone with violent agitation for a period of from about 15seconds up to about two minutes, withdrawing the resultant reactionmixture from said first reaction zone as effluent and passing to asecond reaction zone, maintaining the reaction mixture in said secondreaction zone with gentle agitation for a period of from /2 hour to 2hours, maintaining the temperature in said second reaction zone at from80 C. to C., withdrawing the resultant mixture from said second reactionzone as eflluent, admixing a strong aqueous sodium hydroxide solutionwith said reaction mixture from said second zone to react with all ofthe hydrogen chloride contained therein and to provide a pH therein offrom 8.5 to 11.0 and to form an aqueous phase and a water-immiscibleorganic phase, and separately recovering said organic phase, andrecovering poly primary amines from said organic phase.

7. In a continuous process for producing poly primary aromatic aminecondensation product from aniline and formaldehyde, the steps whichcomprise admixing aqueous hydrochloric acid and aniline, said acid beingadmixed in an amount sufficient to neutralize from about 20 mol percentto about 70 mol percent of said aniline to form aniline hydrochloride,introducing said admixture into a mixing zone, introducing into saidmixing zone with violent agitation, an amount of formaldehyde to providea mol ratio of aniline to formaldehyde of from 1.25:1 to 2.1:1,maintaining the resultant mixture in said mixing zone at not over about40 C., rapidly conducting said resultant mixture to a first reactionzone and there thoroughly intermixing said reactants with continuousviolent agitation, maintaining the temperature of said first reactionzone at below the boiling point of any component therein, maintainingsaid reactants in said reaction zone for from about 15 seconds to about2 minutes, passing the resultant reactant mixture from said firstreaction zone to a second reaction zone, maintaining the reactionmixture in said second reaction zone with gentle agitation at atemperature of from 80 C. to 105 C. for a period of from /2 hour to 2hours, and withdrawing the reacted mixture from said second reactionzone.

8. A process as in claim 1 wherein said first reaction zone comprises aninitial mixing stage and a second, contacting stage and wherein a streamof said aniline-acid salt admixture is thoroughly and violently blendedwith a formaldehyde stream in said initial stage, and said blendedstream is then conducted to said second stage wherein intermixing isless vigorous.

9. Process as in claim 8 wherein said acid is hydrochloric acid and isadmixed in an amount to neutralize from 20% to 70% of said aniline.

References Cited UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No 3 ,478 ,099 November 11 1969 Richard J. Ross et al.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

In the heading to the drawings and in the heading to the printedspecification, in the title, "METHYLENEDIAMILINES" should readMETHYLENEDIANILINES Column 3, line 9, "cantact" shou] read contact line38, "is" should read if Column 4, line 32, "or" should read of Column 5,line 59, "the", second occurrence, should read that Column 6, after line14, insert as the beginning of a new paragraph, The final reactionmixture passing from secondary Column 8, line 2, "volent" should readviolent line 14, "phose" should read phase Signed and sealed this 24thday of November 1970.

(SEAL) Attest I EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. AttestingOfficer Commissioner of Patents

